Alternative oxidant to remove cyanobacteria and cyanotoxins in water treatment plants

OSVALDO ARANDA; FERNANDEZ VERÓNICA; DANIELA SEDAN; LORENA ROSSO; DARÍO ANDRINOLO; LEDA GIANNUZZI

Pilanesberg

Conferencia; 9TH INTERNATIONAL CONFERENCE ON TOXIC CYANOBACTERIA; 2013

Nelson Mandela Metropolitan University

Cyanobacterial toxins are considered as a serious threat to human and environmental health and accumulation of debris can impair operations in water treatments plants. Moreover, control of phytoplankton is a preventive measure which can avoid toxin production The aim of this work was to develop methodologies for cyanobacteria and cyanotoxins removal based on the use of a chemical agent with antioxidant activity, antimicrobial and algaecide effect that leaves no residue in the environment. We worked with a strain of Microcystis aeruginosa in culture (CAAT 2005) DleuMCLR producer. We applied different doses of an oxidizing agent (BIOXI B) provided by the company Sabinur (Buenos Aires, Argentina) at doses of 0, 1, 5, 10, 15, and 20 ppm for different contact times (0, 4, 8, 12, 24 and 48 hours) in the presence of light. During the experiment, samples were taken and evaluated for removal of chlorophyll kinetics, total protein, cell count assessed by inverted microscope, cell viability and the remaining concentration of DleuMCLR. Toxin determination was made by inhibition assay protein phosphatase and HPLC-DAD. It also assessed the bactericidal effect on a culture of E. coli. Minimum Inhibitory Concentration (MIC) required for inhibiting the development of Microcystis aeruginosa in the culture medium was 1.0 ppm of the product. This value causes a decrease in the chlorophyll content of 43% of the initial value. The application of 5.0 ppm of product during 24 hs, a decrease of 67.5% of the initial protein content was observed. Under these conditions the culture viability measured by agar plate counting BG11 was completely inhibited. Treatments with 1.0, and 5.0 ppm of product during 24 hs produces alterations in cell morphology of Microcystis aeruginosa cells given by fading and birefringence inside the cell. Besides bactericidal effect was observed given by complete inhibition of growth of culture of E. coli. The highest percentage DleuMCLR removal is achieved at a concentration of 15 ppm of reducing it to 0.04 ppm of DleuMCLR (94.4% reduction). Our results suggest that this product may be applied in water treatment plants in order to enhance conventional treatments designed to remove cyanobacteria and cyanotoxins.